The House passed a bill Thursday to halt the admission of Syrian refugees into the U.S. until they undergo the toughest vetting process ever developed for people fleeing a war-torn nation.<br />The legislation, passed by a vote of 289-137, was rushed through in response to last week's terrorist attacks in Paris.<br />One of the terrorists is believed to have entered Europe through Greece with a group of Syrian refugees, sparking calls by congressional leaders to "pause" the flow of refugees into the U.S. from Syria and Iraq.<br />The bill requires the nation's three top security officials - the Homeland Security secretary, FBI director, and national intelligence director - to certify to Congress that each Syrian or Iraqi refugee is not a security threat before the refugee can be admitted into the U.S.